Abstract： Background Effect of percutaneous transluminal septal ablation (PTSA) with ethanol injection on electromechanical remodeling of left ventricule still remains unknown. This study was conducted to assess the potential significance of cardiac electromechanical mapping (CEMM) in analyzing the left ventricular remodeling before and immediately after percutaneous transseptal myocardial ablation (PTSMA) in patients with hypertrophic obstructive cardiomyopathy (HOCM).Methods Eight patients with drug-refractory HOCM and 6 patients with hypertrophic cardiopathy (HM) without increased left ventricular outtract gradien (LVOTG) were enrolled into the present study. CEMM was undergone in patients with HOCM before and immediately after PTSA procedure, and in patients with HM. Results PTSA was successful in all patients with HOCM, LVOTG significantly decreased from (62.87±21.16) mmHg to (12.73±3.05) mmHg immediately after ablation procedure. Value of UVP in septal-base segment in HM group was higher than that in HOCM group [(22.79±2.34)mV vs (18.54±1.76)mV].In patients with HOCM, lateral-middle and -base segments had lowest value of UVP [(15.93±1.11) mV and (15.83±1.07)mV] before PTSA. Value of UVP at posterior-middle segment decreased from (23.58±2.21)mV pre-PTSA to (18.89±1.91)mV post-procedure, PTSA led to significant increase of UVP at lateral-middle segment. Septal region in patients with HM and septal-middle, septal-base, posterior-base segments in HOCM had lower value of local linear shortening (LLS) among all patients in both HOCM and HM groups. PTSA resulted in significant reduction of LLS in anterior region and at septal-apex segment. Anterior-base and septal-middle segments in patients with HM had lowest value of local active time (LAT), and significantly differentiated from that in patients with HOCM [(-8.57±0.68)ms vs (-18.61±1.02)ms, (-6.75±0.37)ms vs (-21.90±0.96)ms, respectively].LAT at septal-middle and -base segments in patients with HOCM was decreased significantly [(-21.90±0.96)ms vs (-13.80±1.04)ms, P<0.002; and (-15.20±1.06)ms vs (-6.33±0.52)ms, respectively] immediately after PTSA.Conclusions Posterior-lateral and anterior region probably played important roles in electromechanical remodeling. Significant electromechanical remodeling disassociation (uncoupling) was detected in most left ventricular regions, which would be important in differentiating of HOCM from HM, and in predicting the prognosis in patients with HOCM after PTSA procedure.